Device for automatic cutting of thread in sewing machines

ABSTRACT

A device for the automatic cutting of thread structures used in association with sewing machines having a sole plate, a station plate, a feed plate and a pressure foot, comprises a pneumatic device for sucking in the thread structure which pneumatic device includes a tube located beneath a circular opening in the feed plate, and cooperative cutting elements one mounted at one end of the stitch plate and the other mounted on the feed plate.

United States Patent [1 1 Schips et 1 1 Dec.2, 1975 I DEVICE FOR AUTOMATIC CUTTING OF THREAD IN SEWING MACHINES [75] Inventors: I-Ielmut Schips, Rorschach; Rolf Kernbichler, Urnasch, both of Switzerland [73] Assignee:

[22] Filed.

Helmut Schips, Rorschach,

Switzerland May 9, 1974 [21] Appl. No.: 467,739

[52] U5. Cl 112/252; 112/DIG. 1

[51] .Q D05B 65/02 [58] Field of Search 112/65. 66, 68, 70, 77, 112/252, DIG. 1

[56] References Cited UNITED STATES PATENTS 1,915,551 6/1933 Schramm 112/252 1,962,903 6/1934 Lyons 112/252 2,298,246 10/1942 McCann 112/252 X 2,345,943 4/1944 McCann 112/252 2,376,417 5/1945 Chudner 112/252 2,849,974 9/1958 Tishler et a1... 112/252 X 3.509.838 5/1970 Bowin v. 112/252 X 3,698,336 10/1972 Launer 112/252 3,749,040 7/1973 .lurgens 112/252 FOREIGN PATENTS OR APPLICATIONS 1,685,040 7/1971 Germany 112/252 1,945,310 4/1971 Germany 112/252 Primary Examiner-Werner H. Schroeder Attorney, Agent, or Firm-Browdy and Neimark [57] ABSTRACT A device for the automatic cutting of thread structures used in association with sewing machines having a sole plate, a station plate, a feed plate and a pressure foot, comprises a pneumatic device for sucking in the thread structure which pneumatic device includes a tube located beneath a circular opening in the feed plate, and cooperative cutting elements one mounted at one end of the stitch plate and the other mounted on the feed plate.

7 Claims, 7 Drawing Figures FIG. 6

FIG. 7

DEVICE FOR AUTOMATIC CUTTING OF THREAD IN SEWING MACHINE-S FIELD OF INVENTION The present invention concerns the automatic cutting of thread structures'in sewing machines, and, more particularly, relates to a device for automatically cutting thread in sewing machines having a sole plate, a stitch plate, a feed plate and retaining foot.

BACKGROUND It is known that when so-called chain stitches are used, particularly in tricot goods, the chain stitch is cut by hand after sewing. This is tedious and costly. Mechanical devices contemplated for this purpose have not achieved acceptance in the industry.

SUMMARY OF INVENTION 7 The present invention provides for a pneumatic device to align and blow in or suck in the thread structure, as well as a knife edge mounted at one end of the stitch plate, whose counter cutter is mounted on the feed plate. The present invention thus provides for the effective automatic cutting of thread in sewing machines.

BRIEF DESCRIPTION OF DRAWING A sample embodiment of the subject of the invention is shown in the attached figures.

FIG. 1 shows a cross-section through the actual sewing part of a sewing machine, in the direction of travel of the material, cut through the sewing needle, in the initial position;

FIG. 2 shows a device according to FIG. 1, immediately after the cutting of a thread structure;

FIG. 3 shows the arrangement according to FIG. 1, without needle and shoe in top view, at the moment the suction tube is freed to receive the thread structure;

FIG. 4 shows a stitch plate in cross-section along line IVIV in FIG. 5;

FIG. 5 shows the stich plate according to FIG. 4 in top view;

FIG. 6 shows a top view of the suction tube with the feed dogs below it;

FIG. 7 shows a top view of the thread holder with thread and thread suction tube.

In mass production of articles and clothing, especially tricot underclothing, pieces of material are generally sewn together with flat seams or overcasting stitches.

These seams can be made with the following threads:

-four needle threads four under threads one shuttle thread or four needle threads one under thread one shuttle thread, or

three needle threads one under thread one shuttle thread, or

two needle threads one under thread one shuttle thread, or one-two needles, overcasting stitches.

In order for these seams not to open up at the beginning or end of the sewn material, the chain stitch is turned backward and locked with stitches adjusted to the locking length.

This process has now been mechanized.

In FIGS. 1 and 2, a sole plate 1 on a sewing machine can be seen, with a stitch plate 3 fastened thereto. This stitch plate 3 has a feed plate 5 displaceably mounted on it. In order to hold the fabric on the feed plate 5, a pressure arm 7 having a foot is provided. The foot has an opening 8 in which a needle 9 projects guided by a needle guide 10. The stitch plate 3 is likewise provided with a corresponding opening 4 to allow the needle 9 to pass through, while the feed plate 5 has a corresponding longitudinally extending slot 6. In the vicinity of the opening 4, the stitch plate 3 is provided at its free end with a knife 11 having a cutting edge 12 made of hard metal.

The asembly also includes a suction tube 13 for sucking in a chian stitch. While the stitch plate 3 is fastened to the fixed sole plate 1, the feed plate 5, attached to a feed carrier 15 by means of screws 27, moves to and fro together with the pressure arm 7, in order to bring the material 17 being sewn beneath the needle 9. FIG. 1 also shows a chain stitch 19 within the tube 13 having been sucked therein by suction; the end of the chain stitch, in the position shown in FIG. 2, has just been removed by the suction tube 13.

Feed plate 5, the slot 6 of which is widened to a circular opening in the vicinity of the needle as seen in FIG. 3, also serves as a counterpart to the cutting edge 12 of the knife 11 for cutting the chain stitch 19. Therefore, the corresponding part of the circular recess of the slot 6 is made in the form of a cutting edge 23. The stitch plate 3, shown in FIGS. 4 and 5, serves as a guiding element for the feed plate 5, with the stitch plate 3 having a trapezoidal part, as viewed in cross-section, which fits into a guide groove with conical sides (side walls of slot 6), thus forming a conical guide 25. The feed plate 5 performs the above-mentioned oscillating movement together with the feed carrier 15, the latter of which is provided with a cover lid 16.

In the vicinity of the path of needle 9 and below the stitch plate 3, fixed in position, is mounted in known fashion a looper 30 which serves to knot the thread, with a looper shaft 34 and a shaft bearing block 36. FIG. 6 also shows the top view of the suction tube 13 with chain stitch 32 entering it.

FIG. 7 shows a needle arm 40, which moves the needle 9 up and down in the needle guide 10. A needle thread 42 in a needle guide 46 is also shown. A thread suction tube 45 is located in the vicinity of the point of sewing needle 9.

The device described functions as follows:

According to FIG. I, which shows the starting position of the machine, the seamstress brings the material 17 to be sewed beneath the foot of the pressure arm 7. The chain stitch 19 to be locked by means of the sewing machine is drawn into the correct position by the airstream in suction tube 13 (a compressed air stream can also be used). Chain stitch 19 thus moves automatically into the sewing position and need no longer be wrapped around it by hand as previously. When starting the machine, the pressure arm 7 together with the foot, also referred to as the pressure foot, together with the feed carrier 15 with the feed plate 5, moves from the position shown in FIG. 1 toward the right, reaching the position shown in FIG. 2. During this movement, the cutting edge 23 of the feed plate 5 is pushed beneath the cutting edge 12 of knife 1 1 against the fixed stitch plate 3 and the free end of the chain stitch 19 is cut off, a process which has just taken place as shown in FIG. 2.

The locking length is adjustable on the machine itself (not shown).

FIG. 3 corresponds to the position of the machine as shown in FIG. 1. In this figure, the opening of suction tube 13 is exposed beneath the slot 6 of the feed plate 5, thus allowing the air stream to suck in the chain stitch 19.

FIGS. 4 and 5 show the structure of the stitch plate 3 when it is at rest, with the corresponding trapezoidal parts for guiding the feed plate 5.

By bringing the thread suction tube 45 into the vicinity of the point of the needle 9, the needle thread 42 is sucked away, as soon as the sewing procedure is over. This prevents needle thread 42 from being sucked into suction tube 13 by the air stream, which could cause needle thread 46 to unravel.

The system described above is characterized by its simplicity, insensitivity to possibly disruptive forces and reliability in operation, as well as by the fact that it can be incorporated in existing sewing machines.

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.

What is claimed is:

l. A device for automatic cutting of thread structures of an article in sewing machines having a sole plate, a stitch plate fastened to said sole plate, a feed plate mounted on said stitch plate having a cutting edge, a needle positioned above said feed plate and a pressure foot fastened to said feed plate, said device comprising:

4 pneumatic means positioned under said feed plate for automatically sucking in the thread structure, and for automatically looping the thread around said article;

a cutter element mounted at one end of said stitch plate; and

cooperative cutting means mounted on said feed plate for cooperating with said cutter element for cutting the thread structures.

2. Device according to claim 1 wherein said pneumatic means comprises a tube for pneumatic removal of a cut chain stitch.

3. A device in accordance with claim 2 further comprising a second tube for pneumatic immobilization of the sewing thread.

4. Device according to claim 2, wherein said tube of the pneumatic system used for carrying away the chain stitch extends up to the immediate vicinity of the cutting edge of the stitch plate knife.

5. Device according to claim 1 wherein said feed plate has an opening to allow the needle to pass through, the border of said opening being partially made in the form of a counter cutter.

6. Device according to claim 1, wherein said feed plate is guided on said fixed stitch plate.

7. Device according to claim 1, wherein the opening of the feed plate is slot-shaped and has a circular opening at the end of the slot, which corresponds to the free opening of a tube located thereunder for carrying away the chain stitch. 

1. A device for automatic cutting of thread structures of an article in sewing machines having a sole plate, a stitch plate fastened to said sole plate, a feed plate mounted on said stitch plate having a cutting edge, a needle positioned above said feed plate and a pressure foot fastened to said feed plate, said device comprising: pneumatic means positioned under said feed plate for automatically sucking in the thread structure, and for automatically looping the thread around said article; a cutter element mounted at one end of said stitch plate; and cooperative cutting means mounted on said feed plate for cooperating with said cutter element for cutting the thread structures.
 2. Device according to claim 1 wherein said pneumatic means comprises a tube for pneumatic removal of a cut chain stitch.
 3. A device in accordance with claim 2 further comprising a second tube for pneumatic immobilization of the sewing thread.
 4. Device according to claim 2, wherein said tube of the pneumatic system used for carrying away the chain stitch extends up to the immediate vicinity of the cutting edge of the stitch plate knife.
 5. Device according to claim 1 wherein said feed plate has an opening to allow the needle to pass through, the border of said opening being partially made in the form of a counter cutter.
 6. Device according to claim 1, wherein said feed plate is guided on said fixed stitch plate.
 7. Device according to claim 1, wherein the opening of the feed plate is slot-shaped and has a circular opening at the end of the slot, which corresponds to the free opening of a tube located thereunder for carrying away the chain stitch. 